Flip chip bonding in which bump electrodes also called bumps are formed on a chip and the chip is directly connected to a circuit board has become widely employed as a method of mounting a chip on a circuit board. The flip chip bonding is a method for joining a chip and a circuit board by forming a plurality of bumps (bump electrodes) made of a material such as solder on a circuit side of the chip, and heating and melting the bumps to join the bumps to a plurality of electrodes on a circuit board. As compared to a connecting method using the conventional wire bonding, the flip chip bonding has various advantages such as a reduced area for mounting, excellent electric characteristics, and elimination of necessity for mold sealing.
In the flip chip bonding, in order to ensure reliability of connection at a joining portion between a chip and a circuit board, it is required to perform resin molding of a gap between the chip and the circuit board using an underfill material or the like. However, using an underfill material has a problem that filling of a liquid resin requires times, as well as a problem that it has become difficult to inject a liquid resin under a present circumstance that a gap between a chip and a circuit board has become increasingly smaller. Therefore, there is proposed a bonding method in which resin molding between a chip and a circuit board is performed by applying a non-conductive film (NCF) previously to a surface of the chip, and performing melting and hardening of the resin at the same time as joining between the chip and the circuit board.
According to this method, the non-conductive film (NCF) is previously applied to the surface of the chip, and after the chip is suctioned to a holding member and picked up along with the non-conductive film (NCF), the chip is flipped by rotating the holding member, so that the side of the non-conductive film (NCF) faces downward. Then, a bonding tool is brought into contact with the side of the chip opposite of the side to which the non-conductive film (NCF) is applied and caused to suction the chip, and thus the chip is passed from the holding member to the bonding tool. Therefore, when the chip is transferred, the side of the chip to which the non-conductive film (NCF) is applied is in contact with an upper surface of the holding member, and the chip passed to the bonding tool has its side of the non-conductive film (NCF) face downward (the side of the circuit board). Thereafter, when the chip is pressed to the circuit board with the bonding tool, and the temperature of the bonding tool is increased up to the melting temperature of bumps (about 300° C.), the non-conductive film (NCF) melts at the same time as the bumps melt and comes between the chip and the circuit board. Then, after the bonding tool is moved upward, the temperature of the bumps and the non-conductive film (NCF) decreases and the metal of the molten bumps and the molten resin are hardened, and the bonding of the chip to the circuit board is completed.
Upon completion of the bonding, the bonding tool is heated as high as about 300° C. Therefore, if the bonding tool receives a chip coming next from the holding member at this temperature, the non-conductive film (NCF) applied to a chip surface (the side of the holding member) is heated and molten, and then adversely attached to a surface of the holding member when the bonding tool at high temperature is brought into contact with the chip. Accordingly, it is necessary to perform bonding after the bonding tool at high temperature is cooled down below the melting temperature of the non-conductive film (NCF) (e.g., about 50° C.), then the bonding tool receives a chip coming next from the holding member, and the temperature of the bonding tool is increased again. However, as the bonding tool is generally cooled using air at normal temperature (about 25° C. to 30° C.), it takes time to cool the bonding tool at the temperature as high as about 300° C. down to about 50° C. This results in a problem of increased bonding time as a whole.
Therefore, there is proposed a method for reducing bonding time by continuing bonding without cooling the bonding tool in a manner such that the chip is passed from the holding member to the bonding tool while being suctioned to the surface of the bonding tool in a state in which the holding member and the bonding tool are not in contact with each other, i.e., in a state in which transmission of heat to the holding member from the bonding tool is blocked.